The present invention relates to a system for draining shed blood from the body cavity of a patient and reinfusing clean, filtered blood back to the patient, and more specifically to a chest drainage unit (CDU) that includes a progressive filtration system for filtering out blood clots and other contaminants at both the inlet and outlet ports inside the CDU's collection chamber. More particularly, this invention relates to a high flow, micron filter assembly that refilters blood that collects at the bottom portion of the collection chamber prior to reinfusion to the patient with the assembly further including a drop tube that permits the refiltered blood to exit at an outlet port located at the top portion of the CDU.
A CDU is an apparatus for suctioning gases and liquids from the pleural cavity of patients. The pleural cavity lies within the rib cage above the diaphragm and is surrounded by the pleural membrane. The pleural cavity contains both lungs, which in their normal expanded state fill the pleural cavity. Several conditions and diseases such as interventional surgery, trauma, emphysema and various infections can cause a build up of liquid and gases around the lungs in the intrapleural space. When this happens, it causes the lungs to collapse to a volume much less than that of the pleural cavity, thereby severely impairing breathing functions of the patient. The lungs can be re-expanded to their normal state to fill the pleural cavity by draining the liquid and gases from the intrapleural space using a CDU.
CDUs are also used during autotransfusion for recovering autologous blood from the patient's pleural and mediastinal cavities and transfusing that blood back into the patient. Autotransfusion offers significant advantages over normal transfusion procedures which use homologous blood from other humans. Autologous blood reduces the risk of adverse reactions and transmission of infectious disease while supplying a readily available and safe source of compatible blood to the patient. For these reasons, CDUs are being designed to both evacuate fluids from the intrapleural space and autotransfuse shed autologous blood back into the patient.
Various devices have been developed to drain and collect fluids such as blood from the intrapleural space for subsequent autotransfusion. U.S. Pat. No. 4,114,416 to Karwoski et al. illustrates the prior art development of autotransfusion CDUs. The device includes a collection chamber for the collection of fluid from the pleural cavity, a water seal chamber for preventing passage of gas from the atmosphere into the patient's pleural and mediastinal cavities, and a manometer chamber for regulating the degree of vacuum in the system. An inlet port of the collection chamber is connected to the patient's pleural cavity via a thoracotomy tube that deposits shed blood and gases into the collection chamber. As the shed blood enters the inlet portion of the collection chamber, a large area gross filter, such as a fabric or an open-pore sponge filter, is used to remove blood clots and gross particles from incoming fluids. Once filtered, the blood collects at the bottom portion of the collection chamber until reinfusion is effected and the blood is drained through an outlet port located at the bottom portion of the collection chamber. The Karwoski et al. device is also placed in fluid flow communication with a blood compatible pump set through tubing that connects the pump to the outlet port and permits the collected blood to drain therethrough for reinfusion to the patient.
One drawback with the Karwoski et al. device is that no provision is made for refiltering the collected blood inside the collection chamber just prior to reinfusion. As collected blood rests at the bottom portion of the collection chamber prior to reinfusion, the blood can begin to coagulate and develop blood clots as the fibrinogen within the blood converts into fibrin, thereby entrapping red blood cells with the coagulated blood plasma. If the blood clots are not removed or filtered out after the blood has collected inside the collection chamber, the tubing between the patient and the outlet portion of the collection chamber will become clogged and unusable as the blood exits the Karwoski et al device. Further, a microaggregate filter that is normally interposed between the outlet of the collection chamber and the patient can also become clogged if clots are not refiltered prior to exiting the collection chamber. As a result, a practitioner must take the time to replace the entire blood infusion set which exposes the patient to undesirable risks, such as infection, caused by the time delay in clearing or replacing the fluid pathway between the CDU and the patient and reestablishing the autotransfusion process. Moreover, interruption of the autotransfusion process might require the practitioner to substitute homologous blood that could be contaminated or incompatible with the patient's own blood.
Another drawback with the Karwoski et al. device is that blood for reinfusion must be withdrawn from an outlet port located at the bottom portion of the collection chamber. The problem with this bottom location of the outlet port is that it necessarily requires that extra tubing be provided to properly secure and orient the drip chamber that is normally in fluid flow communication with the tubing leading from the outlet port. The drip chamber is normally interposed between the device and the infusion pump and provides the practitioner with a visual indication that fluid flow is being maintained inside the tubing. In contrast, when the outlet port is located at the top portion of the collection chamber, no additional tubing is required since having the outlet port located at the top portion of the device removes the need for additional tubing needed to properly secure and orienting the drip chamber.
As of yet, nothing in the prior art has addressed the problem of refiltering collected blood as it exits the collection chamber of the CDU prior to reinfusion back to the patient. Specifically, there has been no design consideration for the filtering out of blood clots that later develop in the blood during storage inside the collection chamber prior to reinfusing that blood back to the patient. Further, there has been no design consideration for pumping collected blood from the top portion of the collection chamber in order to promote a more efficient set up between the infusion pump and the CDU during the autotransfusion process.
There therefore exists a need in the art for a filtration system for removing later developing clots from blood collected at the bottom portion of the collection chamber and exiting that refiltered blood from an outlet port located at the top portion of the collection chamber during the autotransfusion process.